Thermal Behavior of Radial Foil Bearings Supporting an Oil-Free Gas Turbine: Design of the Cooling Flow Passage and Modeling of the Thermal System

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Donghyun Lee ◽  
Hyungsoo Lim ◽  
Bumseog Choi ◽  
Byungok Kim ◽  
Junyoung Park ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbine ◽  
Air Flow ◽  
Successful Implementation ◽  
Flow Passage ◽  
Foil Bearings ◽  
Operation Speed ◽  
Bearing Sleeve ◽  
Cooling Air Flow ◽  
Cooling Air

Gas foil bearings (GFBs) have many noticeable advantages over the conventional rigid gas bearings, such as frictional damping of the compliance structure and tolerance to the rotor misalignment, so they have been successfully adopted as the key element that makes possible oil-free turbomachinery. As the adoption of the GFB increases, one of the critical elements for its successful implementation is thermal management. Even though heat generation inside the GFB is small due to the low viscosity of the lubricant, many researchers have reported that the system might fail without an appropriate cooling mechanism. The objective of the current research is to demonstrate the reliability of GFBs installed in the hot section of a micro-gas turbine (MGT). For the cooling of the GFBs, we designed a secondary flow passage and thermohydrodynamic (THD) analysis has been done for temperature prediction. In the analysis, the 3D THD model for the radial GFB extended to include the surrounding structure, such as the plenum, chamber, and the rotor in the solution domain by solving global mass and energy balance equations. In the MGT, the pressurized air discharged from the compressor wheel was used as the cooling air source, and it was injected into the plenum between two radial GFBs. We monitored the pressure and temperature of the cooling air along the secondary flow passage during the MGT operation. No thermal instability occurred up to the maximum operation speed of 43,000 rpm. The test results also showed that the pressure drop between the main reservoir and the plenum increases with an increasing operation speed, which indicated an increased cooling air flow into the plenum. The plenum and bearing sleeve temperature was maintained close to the cooling air source temperature for the entire speed due to a sufficient cooling air flow into the bearing. In addition, the direct injection of the cooling air from the main stream lowered the bearing sleeve temperature by 5–20 °C over the injection through the reservoirs. The predicted plenum and bearing sleeve temperatures with the developed THD model show good agreement with the test data.

Cooling Air Flow Characteristics in Gas Turbine Components

1982 ◽  
Vol 104 (2) ◽  
pp. 275-280 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (i) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (ii) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

scholarly journals Off-Design Evaluation of a Multiple Expansion Reheating Gas Turbine in Cogeneration Applications

1991 ◽  
Author(s):  
Erio Benvenuti ◽  
Roberto Bettocchi ◽  
Giuseppe Cantore ◽  
Giorgio Negri Di Montenegro
Keyword(s):  
Gas Turbine ◽  
Air Flow ◽  
Thermal Power ◽  
Operational Flexibility ◽  
External Cooling ◽  
Heat Requirements ◽  
Cooling Air Flow ◽  
Performance Results ◽  
Air Control ◽  
Cooling Air

The multiple expansion reheating gas turbine proves to have a potential of good operational flexibility for the intrinsic capability of responding to variations in electric and thermal power demands without appreciable impact on efficiency. The present study deals with evaluation of the performance attainable in off-design operation, with power control obtained through changes in the first and second combustor firing temperatures and in the compressor intake air flow achieved by means of variable inlet guide vanes. Because of the important impact of the hot part cooling air flows on performance, the study includes also a hypothesis of controlling such flows in off-design operation through external means. The predicted off-design performance results superior in the hypothesis of external cooling air flow control, thus making such a system worthy of consideration for possible future developments of machines in this category. To evaluate the suitability of the multiple expansion reheating gas turbine in cogeneration applications, the electric efficiency and the electrical index have been taken into consideration. The capability of varying the reheating temperature represents an effective way of controlling the electrical index with good efficiencies in industrial cogeneration with strongly varying electric power and process heat requirements. With regard to the cooling air control through external means, implementation of such a more complex system seems to be avoidable at least when the gas turbine is intended specifically for application in cogeneration, because of its smaller impact on the overall efficiency of the system.

scholarly journals Cooling Air Flow Characteristics in Gas Turbine Components

1981 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (1) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (2) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

Analysis of Effect of Advanced Technique Configurations on Overall Performance of High Bypass Turbofan Engine

2014 ◽  
Author(s):  
Liu Jian Jun
Keyword(s):  
Air Flow ◽  
Engine Performance ◽  
Performance Model ◽  
Direct Drive ◽  
Nozzle Throat ◽  
Advanced Technique ◽  
Turbofan Engine ◽  
Overall Performance ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical study was undertaken using the performance model of a two spool direct drive high BPR 300kN thrust turbofan engine, to investigate the effects of advanced configurations on overall engine performance. These include variable bypass nozzle, variable cooling air flow and more electric technique. For variable bypass nozzle, analysis on performance of outer fan at different conditions indicates that different operating points cannot meet optimal performance at the same time if the bypass nozzle area kept a constant. By changing bypass nozzle throat area at different states, outer fan operating point moves to the location where airflow and efficiency are more appropriate, and have enough margin away from surge line. As a result, the range of variable area of bypass nozzle throat is determined which ensures engine having a low SFC and adequate stability. For variable cooling airflow, configuration of turbine cooling air flow extraction and methodology for obtaining change of cooling airflow are investigated. Then, base on temperature analysis of turbine vane and blade and resistance of cooling airflow, reduction of cooling airflow is determined. Finally, using performance model which considering effect of cooling air flow on work and efficiency of turbine, variable cooling airflow effect on overall performance is analyzed. For more electric technique, the main characteristic is to use power off-take instead of overboard air extraction. Power off-take and air extraction effect on overall performance of high bypass turbofan engine is compared. Investigation demonstrates that power offtake will have less SFC.

scholarly journals Analysis of the energetic/environmental performances of gas turbine plant: Effect of thermal barrier coatings and mass of cooling air

2009 ◽  
Vol 13 (1) ◽  
pp. 147-164 ◽  
Author(s):  
Ion Ion ◽  
Anibal Portinha ◽  
Jorge Martins ◽  
Vasco Teixeira ◽  
Joaquim Carneiro
Keyword(s):  
Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Heat Transfer Analysis ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings ◽  
Cooling Air Flow ◽  
Cooling Air

Zirconia stabilized with 8 wt.% Y2O3 is the most common material to be applied in thermal barrier coatings owing to its excellent properties: low thermal conductivity, high toughness and thermal expansion coefficient as ceramic material. Calculation has been made to evaluate the gains of thermal barrier coatings applied on gas turbine blades. The study considers a top ceramic coating Zirconia stabilized with 8 wt.% Y2O3 on a NiCoCrAlY bond coat and Inconel 738LC as substrate. For different thickness and different cooling air flow rates, a thermodynamic analysis has been performed and pollutants emissions (CO, NOx) have been estimated to analyze the effect of rising the gas inlet temperature. The effect of thickness and thermal conductivity of top coating and the mass flow rate of cooling air have been analyzed. The model for heat transfer analysis gives the temperature reduction through the wall blade for the considered conditions and the results presented in this contribution are restricted to a two considered limits: (1) maximum allowable temperature for top layer (1200?C) and (2) for blade material (1000?C). The model can be used to analyze other materials that support higher temperatures helping in the development of new materials for thermal barrier coatings.

Improvements to the Performance of a Prototype Pulse, Pressure-Gain, Gas Turbine Combustor

1990 ◽  
Vol 112 (1) ◽  
pp. 67-72 ◽  
Author(s):  
J. A. C. Kentfield ◽  
L. C. V. Fernandes
Keyword(s):  
Secondary Flow ◽  
Gas Turbine ◽  
Pulse Pressure ◽  
Path Length ◽  
Flow Path ◽  
Maximum Pressure ◽  
Gas Turbine Combustor ◽  
Flow Passage ◽  
Delivery Pressure ◽  
Flow Path Length

A description is given of a simple, prototype, pulse, pressure-gain combustor for a gas turbine. The work reported was targeted at alleviating problems previously observed with the prototype combustor. These were related to irreversibilities, causing a performance deficiency, in the secondary flow passage. The work consisted of investigating experimentally the effect of tuning the secondary-flow path length, adding a flow restrictor at the combining-cone entry station, and redesigning the combining cone itself. The overall result was to eradicate the previously noted performance deficiency, thereby increasing the maximum pressure gain obtained in the gas turbine from 1.6 to 4.0 percent of the compressor absolute delivery pressure.

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